1. Field of the Invention
The present invention relates to a humidity sensitive resistor wherein a change of humidity is detected as the variation of electrical resistance, and especially relates to a humidity sensitive resistor wherein a macromolecular resin film is used as a humidity sensitive film.
2. Description of the Prior Art
Hitherto humidity sensitive resistors are known such as a so-called Dunmore type humidity sensitive resistor wherein electrolytes, for example, lithium chloride (LiCl) are coated on the surface of the insulating substrate, a humidity sensitive resistor which is composed of an organic macromolecular electrolyte film, and so on.
In the conventional humidity sensitive resistor, the impedance between detecting electrodes changes by means of ionization of lithium chloride due to moisture absorption. The latter humidity sensitive resistor takes advantage of the hygroscopic property and ionconductivity of the macromolecular electrolyte film, and the impedance between detecting electrodes changes in the same manner. However, since all humidity sensitive resistors have hydrophilic character, these humidity sensitive resistors are dissolved owing to absorption of water in high humidity or dew fall condition, so that these humidity sensitive resistors suffer the disadvantage such as the poor water resisting property and lack of operation stability. For improving these disadvantages, an attempt to cross-link a film composed of hydrophilic polymer or macromolecular electrolyte can be considered. But, on the contrary, a drop of responsibility is caused when humidity sensitive resistors possess the water resisting property with the aid of cross-linked structure, so that a lowering of the detection characteristic is produced. Therefore, this is not considered as a preferred solution of the problem.